1. Field of the Invention
The present invention relates to a bias controlling apparatus; and, more particularly to a bias controlling apparatus capable of automatically controlling an error of bias power generated during the change of temperature or the manufacturing thereof.
2. Description of the Related Art
In general, a power amplifier has been used for transceiving a signal with a wireless in a wireless communication system such as a mobile communication terminal. Herein, the power amplifier means a device to supply a load through an antenna by efficiently amplifying a fine signal into a large signal with a small distortion.
Since such power amplifier includes a CMOS power amplifier designed by a GaAs process as a special semiconductor and a commercial CMOS process, the CMOS power amplifier can be mass-produced, be cheap in production cost and have various application fields.
Meanwhile, a power controller of the power amplifier has been developed in order to stably control the operation of the power amplifier, and various technologies have been studied and developed in order to further stably supply the power to the power amplifier using the power controller.
A conventional power amplifying system includes a voltage controller to supply a constant voltage corresponding to a reference voltage to the power amplifier, a current controller to control a driving current according to the inputted control voltage and a bias controller to control a bias power applied to the power amplifier by using the driving voltage and the driving current, wherein a stable current is supplied to the power amplifier by appropriately controlling the bias power according to the inputted control voltage.
However, although the characteristics of the power amplifier cannot be changed since the power amplifier performs an amplification of power in an appropriate operation region at a normal temperature, if the temperature is changed, the characteristics of the power amplifier becomes changed according to the temperature; and, therefore, there occurs a problem such as a deterioration of performance.
More specifically, since the operation characteristics of the power amplifier is sensitively changed according to the change of the applied bias power, the bias power may be easily changed due to the temperature change or the process change during the manufacturing thereof.
Accordingly, although the performance of the power amplifier is improved by controlling the bias power applied to the power amplifier, since a compensation circuit to control the applied bias power does not exist in the prior art, there is a problem to degrade the characteristics of the power amplifying system.
Therefore, there has been required for a method capable of appropriately controlling the bias power of the power amplifier which can be varied due to the temperature change or the process change during the manufacturing processes.